Cardiac defibrillation in humans requires the delivery of an electrical pulse that is several milliseconds long with peak currents as high as 25 amperes. The total energy in such a pulse is about 30 Joules. In order to deliver such a high current, a capacitor is charged up to a voltage on the order of 750 volts.
Various special batteries have been developed to supply such a high current to charge the capacitor. However, the batteries in use comprise low energy density batteries which occupy a large volume within the defibrillator. In defibrillator devices, the combined volume of the battery and the capacitor(s) is greater than the electronics. Therefore, any reduction in battery size or weight provides significant enhancements to an implantable defibrillator.